The embodiment relates to a light emitting device, a light emitting device package, and a lighting system.
A light emitting device (LED) includes a p-n junction diode having a characteristic of converting electric energy into light energy. The p-n junction diode can be formed by combining group III-V elements of the periodic table. The LED can represent various colors by adjusting the compositional ratio of compound semiconductors.
When forward voltage is applied to the LED, electrons of an n layer are bonded with holes of a p layer, so that energy corresponding to an energy gap between a conduction band and a valance band may be generated. This energy is mainly realized as heat or light, and the LED emits the energy as the light.
A nitride semiconductor represents superior thermal stability and wide band gap energy so that the nitride semiconductor has been spotlighted in the field of optical devices and high-power electronic devices. In particular, blue, green, and UV light emitting devices employing the nitride semiconductor have already been developed and extensively used.
According to the related art, current may flow reversely when electrostatic discharge (ESD) occurs, thereby causing a damage to an active layer formed in a light emitting area.
In order to prevent the LED from being damaged by the ESD, according to the related art, a Zener diode is mounted in a package by connecting the Zener diode parallel to the package in the reverse direction of the LED. Thus, when constant voltage is applied, current flows to the LED so that the LED emits the light. In addition, when the ESD occurs, the current flows to the Zener diode so that the LED can be prevented from being damaged.
However, according to the related art, the Zener diode is mounted in the package, so that light absorption may be lowered.